1. Field of the Invention
The present invention relates to a bending-detection apparatus detecting a bending deformation when a sheet-shaped substrate is bent.
2. Description of the Related Art
Conventionally, a bending-detection apparatus in which a bending deformation of a substrate occurred in an external force acted is detected by a piezoelectric transducer being one kind of machinery (distortion) electrical conversion elements has been known. For example, the detecting apparatus (an external force detection sensor) written in Japanese Patent Application Laid-open No. H10-54842 is provided on a piezoelectric board in a cantilever shape, and has a piezoelectric supporting beam (the substrate) in which a plurality of grooves parallel each other are formed in the surface of the piezoelectric board and a plurality of electrodes formed respectively in the plurality of grooves of the piezoelectric supporting beam. The lead-out directions of two adjacent electrodes of the plurality of electrodes are mutually opposite direction, and the electrodes whose lead-out directions are same conduct each other. Namely, it is configured such that two kinds of comb tooth shaped electrodes consisting of the electrodes conducting each other exist on the surface of the piezoelectric supporting beam, and these two kinds of tooth shaped electrodes are disposed alternately thereon.
Suppose that stretch or compression is occurred in a direction perpendicular to the electrodes extending direction in a portion sandwiched between the two kinds of electrodes on the surface of the piezoelectric supporting beam when a bending deformation is occurred in the piezoelectric supporting beam by an external force in the detecting apparatus in Japanese Patent Application Laid-open No. H10-54842. When the piezoelectric supporting beam is polarized in a direction perpendicular to the extending direction of the electrodes, the deformation direction of the piezoelectric supporting beam (a stretch direction) becomes parallel to the polarization direction. Therefore, an electric field in a direction perpendicular to the extending direction of the electrodes is obtained between the two kinds of electrodes, and then a voltage (a potential difference) is generated between the electrodes. This makes it possible to detect a bending deformation occurred in the piezoelectric supporting beam.